Third type of ancient human interbred with our ancestors

Posted by Emma Woollacott

Researchers have discovered that a recently-discovered type of ancient human interbred with our ancestors.

An international team used a combination of genetic data and dental analysis to establish that a population living in Asia only 30,000 years ago and dubbed 'Denisovans' contributed four to six percent of their genetic material to the genomes of present-day New Guineans.

The conclusion is based on genetic analysis of the finger bone of a five-to-ten-year-old girl and a single tooth, both found in Siberia's Denisova Cave.

"The fact that Denisovans were discovered in Southern Siberia but contributed genetic material to modern human populations from New Guinea suggests that Denisovans may have been widespread in Asia during the Late Pleistocene," says David Reich, an associate professor at Harvard Medical School who led the population genetic analysis.

Until last year, most scientists believed that modern humans inherited essentially their entire DNA makeup from Neanderthal-related individuals when they migrated from Africa 40,000-55,000 years ago. It was believed that they completely replaced the humans who migrated before them, including Neanderthals.

But sequencing and analysis of the Neanderthal genome earlier this year showed that Neanderthals were not completely replaced, but instead contributed as much as four percent of their genetic material to all modern non-Africans before dying out.

"We have now found evidence for a second gene flow event as well from a different source population and into a narrower set of modern human groups," said Reich."The first gene flow event appears to have been from a population closely related to the Neanderthals, while the second gene flow event was from a population much more closely related to Denisovans."

The new research suggests rather than being an unusual event,, intermixing between diverged human populations may have been common. "In combination with the Neanderthal genome sequence, the Denisovan genome suggests a complex picture of genetic interactions between our ancestors and different ancient hominin groups," said Svante Pääbo of the Max Planck Institute of Evolutionary Anthropology.